Agreed on the B787, but carriers will always go with the limit criteria, as in whats the largest equipment that will serve the airport and therefore can this equipment meet the needs of a full service. The B773 is capable to the ME - Etihad did it during the ash cloud from DUB to AUH presumably on a once off. Weather that was load limited I dont know, in fairness I doubt it was as that would kind of defeat the purpose.
Im guessing if a runway extension was approved in the morning it would take at least 4 years to complete knowing the various qangos and hoops that would have to be jumped through. 2013/2014 is of little interest to AI, they would need it before. Perhaps that would even rule BHX out ?